Effect of polymerization on thermodynamic parameters of melting and stabilization of F-actin structure in normal and dystrophic canine myocardium

Abstract

Differential scanning microcalorimetry was used to determine changes in enthalpy, entropy, and free energy of melting of purified myocardial fibrillar (F) actin from normal dogs and dogs with 2–3-month L-thyroxin-induced and athyreotic cardiomyopathy. Polymerization of globular (G) actin stabilizes protomer structure in both pathologies. However, the conformational changes in actin monomer caused by L-thyroxin-induced and, especially, by athyreotic cardiomyopathy decrease the free energy of the bonds between protomers in the synthesized F-actin. Binding energy between actin protomers modified in athyreotic cardiomyopathy (−12 kJ/mol) is 4 times below the control value (−48.7 kJ/mol), while in L-thyroxin-induced cardiomyopathy it little differs from the normal value (−40.8 kJ/mol).